The present invention relates generally to socket connectors, and more particularly to solder ball connectors of reduced dimension.
Conventionally, when a semiconductor device such as an IC or an LSI (Large Scale Integrated Circuit) is connected to a circuit board such as a printed circuit board, terminals of the semiconductor device are electrically connected to conductive traces of the circuit board via a socket attached to the circuit board. Also, when inspecting electric characteristics of a packaged semiconductor device in an assembly process, terminals of the packaged semiconductor device are connected to a circuit board for inspection in which a circuit for inspection is formed, via a socket for inspecting the semiconductor device (for example, refer to Japanese Patent Application Laid-Open (Kokai) No. 2005-158536).
FIG. 9 is a cross-sectional view of a conventional socket. Such a socket uses a base board 301 for connecting the terminals of a semiconductor device to traces 306 of the circuit board 304. A sliding board 302 which slides laterally and a cover member 303 which is movable vertically are provided above the base board 301. The base board 301 is formed from an insulating material and includes a number of dent portions 307 to accommodate contacts 305.
The contacts 305 are formed from a conductive metal plate and have a unique shape. The body portion of each contact 305 is accommodated in a dent portion 307, and two leg portions of the contact 305 project upward from the dent 307. The two leg portions are arranged to extend across a partition 308. The lower end portion of the contact body portion contacts each of the circuit board traces 306, and the two leg portions contact a terminal (not shown) of the semiconductor device, for example, a solder ball. Therefore, each terminal of the semiconductor device contacts a trace of the circuit board 304. In this case, since the tips of the two leg portions hold the terminal from both sides thereof as if they are sandwiching the terminal, and thus a connection between the two leg portions and the terminal is obtained.
However, in such a conventional socket, the tips of the leg portions sandwich the terminal of the semiconductor device by using the elastic force of the contact 305, i.e., spring force of the contact 305, and therefore, if the spring force of the contact 305 is weak, it becomes difficult to maintain electric connection state between the contact 305 and the terminal. In recent years, as semiconductor devices have been increasingly smaller, a pitch between terminals has also been smaller, and accordingly, a pitch between contacts 305 of the socket should also be smaller. Therefore, the size of the contacts 305 need to be reduced, and the contacts 305 must become thinner. The spring force of the contact 305 becomes weaker, and often the leg portions of the contact 305 cannot hold and sandwich the terminal with sufficient force. As the density of terminals of the semiconductor device increases, the number of terminals also increases. Therefore, it becomes important to absorb distortion between a surface where a number of contacts 305 is aligned, and the circuit board 304 or the cover member 303.